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RV-9 and aerobatics

pierre smith

Well Known Member
Hi guys,
A friend of mine told me the other day that you can in fact do aerobatics in the 9. He said that Van couldn't get the airplane to recover from a six-turn spin in less than 1 1/2 turns and THAT is why he says 'no aerobatics', not because the spar or structure can't handle the g's.
Comments anyone? :cool:
 
pierre smith said:
Hi guys,
A friend of mine told me the other day that you can in fact do aerobatics in the 9. He said that Van couldn't get the airplane to recover from a six-turn spin in less than 1 1/2 turns and THAT is why he says 'no aerobatics', not because the spar or structure can't handle the g's.
Comments anyone? :cool:

I've had friends tell me a lot of foolish things. I think it is worth consideration of who is more qualified to speak, the aircraft designer or a friend who may have heard something.

Your friend's description actually sounds like it may refer to the testing of the RV-6, which probably would not meet spin recovery standards to be certified in the aerobatic category.

And you can, in fact, do aerobatics in an RV-9. In my opinion, it would not be a wise thing to do as the design strength margins are not there.
 
The 1 1/2 turn spin thing was a problem with the -7

They actually put out a service bulletin to replace the -7 rudder with the -9 rudder as an option as the -7 actually had better spin recovery with the larger -9 rudder.

I think I would stick with Van on this one, he really knows what he had in mind with each design and I'm convinced he knows what he is talking about.
 
It occurred to me today while I was practicing lazy-eights and chandelles in my 9A that maybe Van's big announcement at Osh will be:

*An aerobatic wing upgrade for the 9/A*

So much weight is wasted in airplanes (upholstery, fancy panels, thick paint etc.), that strengthening the wing structure by beefing up the spars might only be a 25-50 lb penalty that could be recovered by cutting back everywhere else.

Each wing weighs about 75 lbs (my estimate). a 33% increase in structural weight is only 25 lbs per wing. Using a simple linear relationship, that would take it from a +3.8G to a +5G aircraft.

Of course, nothing is a simple as it seems.

Vern Little 9A
 
Not even spins in a -9

While reading the RV-9 building instructions for details to add to my POH I noticed the -9 is not even approved for spins. That is a big disappointment for me since I really enjoy doing them.

At SnF I asked Mike Seeger (sp?) about spinning the -9, this was before I read the above, and he said it wouldn’t be a problem and that the -9 spins very nicely. Or something like that.
 
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You CAN do whatever your skills and the control deflection will allow. I understand that most airplanes will do a roll.

But, should you? I wouldn't. Even great acro pilots occaisionally screw up, and need an agressive pull out...falling into a split s at the bottom of a roll is a good example. Not alot of G margin or speed/flutter margin there.
 
Clip-wing 9?

Consider this. The 9 has a long wing and if it were cut shorter.....say around 24-25 feet, it still should stall slower than the 6's or 7's with that high-lifting Roncz airfoil and slotted flaps. The bending moment would be lessened ala clipped-wing Cub, probably the cheapest way to make an airplane aerobatic!
More speed/aerobatic/somewhat STOL. ;)
 
Not as strong

pierre smith said:
Hi guys,
A friend of mine told me the other day that you can in fact do aerobatics in the 9. He said that Van couldn't get the airplane to recover from a six-turn spin in less than 1 1/2 turns and THAT is why he says 'no aerobatics', not because the spar or structure can't handle the g's.
Comments anyone? :cool:
Bottom line is the RV-9(a) is not as strong.

Here are the load factors:

+3.8g to ?1.5g for the normal operational category;
+4.4g to ?2.2g for the utility category (which includes most training aircraft); and
+6.0g to ?3.0g for the aerobatic category.​


When Van was designing the plane he designed it for +4.4 g not +6.0 g, as well the negative load factor of -2.2 g not -3.0g was used. Not sure about the spin issue.

Not sure why folks who want to do acro or use 360's don't build a RV-7(a).
 
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"Not sure why folks who want to do acro or use 360's don't build a RV-7(a)."

Agree, and disagree...

Every choice is a compromise to some extent. If the primary goal is to go a little faster or fly upside down in excess, the 7 or 8 is obviously the better choice. However, if efficiency and cross country cruises are the primary goals, the 9 might be the better choice, even if we want to play once-in-a-while within safe limits.

Regarding the 360's "extra" hp- I see the issue more as the desire to climb quickly when needed, esp at a high density altitudes common in the West. We all know that one needs to limit peak speeds (in turbulence) when excess power is available in reserve. If the extra power is available, while keeping the weight low as comapared to factory 0-320 specs (as with a rotary... :D ), it seems to me we just might have the best of both worlds.

Bottom line, with equal power, I dont see a lot of performance difference between the 7 and 9's capabilities, at least at the top end of the speed spectrum. In normal flight, slow or at cruise, (I believe) the 9 has a slight advantage- especially with a light adjustable prop like the IVO.
 
You guys are overlooking another small factor; your operating limitations should prohibit aerobatics. If your DAR includes aerobatics in your operating limitations he is doing you a disservice. The aircraft designer specifically prohibits aerobatics in the -9, and the DAR should hold to that unless you can show considerable documentation to prove that they should be allowed.
 
Mel is that not exactly what phase 1 is about? Documenting the limitations? If a builder wants to demonstrate aerobatics in is rv-9, or lancair columbia demonstrator(done at SnF this year with Sean Tucker at the controls), then can he not do that?

Virtually any experimental could do loops, rolls, hammerheads and many other aerobatic maneuvers without ripping the wings off... Regardless of what a supplier of parts recommends.

Regardless of the merits of whether or not one should or shouldnt. Regardless of any skill the pilot may or may not have.

So as an example. I have totally gone against every thing Vans stands for and put a rediculas engine on a plane not designed for it. Also I have taken it far beyond speeds they recommend, loaded far beyond thier recommended limits, and g'd er up at weights also not recommended. So... Given all that, if I run a phase 1 and doc all that and Im good to go, which I have... THen whats the difference?

Its not the DAR's job to keep the pilot from doing something the plane was not designed for is it? The DAR's job is to see if its safe for flight.

As another example. If I take a lawnmower and rig a drive unit to a prop, mount a hang glider to it, and apply for an airworthness certificate... And the DAR deems it airworthy, and I go do aerobatics with it.... Can the DAR say no in the op lims before it is even proven one way or the other?

Bottom line is I don't see the DAR's job being to determine the limits of the plane. Those limits are demonstrated by the builder.

As another example, Burt never sold his Long EZ as an aerobatic plane, yet there are Long EZ's performing in airshows in frot of the plublic... Another example of a builder demonstrating the capibilities in phase 1 and flying it that way.

Where am I wrong?
 
Clipped wing -9

An old thread here but it got me wondering if anyone has tried what Pierre said to the -9 wing? If so, what was your experience/ feedback?



Consider this. The 9 has a long wing and if it were cut shorter.....say around 24-25 feet, it still should stall slower than the 6's or 7's with that high-lifting Roncz airfoil and slotted flaps. The bending moment would be lessened ala clipped-wing Cub, probably the cheapest way to make an airplane aerobatic!
More speed/aerobatic/somewhat STOL. ;)
 
An old thread here but it got me wondering if anyone has tried what Pierre said to the -9 wing? If so, what was your experience/ feedback?

While I like the thought of this mod, I doubt it has been done. The reason is the pre-punched spar. The -7 and -9 have the same number of ribs, with more space between each on the -9. To do this, you would want to start by respacing the ribs to match that of the -7. Then you can cut down the flaps while keeping the ailerons the stock length. That right there would probably increase the stall speed to close to that of the -7.

You could take close to two feet off the wingspan by changing the wingtips.

After all that you still have a very large HS to deal with. The HS is so large to compensate for the downward pitching moment that occurs when deploying the -9's large fowler flaps.

Here is a list of just some of the reasons I have heard over the years as to why the -9 is NOT aerobic:

1. The wing is too long.
2. The flaps will fail, if you go negative.
3. The VS and rudder aren't strong enough.
4. The HS is weak.
5. The fuselage isn't designed for it.
6. The engine mount will fail.

Also, my operating limitations includes acrobatics. The FSDO inspector made a big point of telling me because he knew all "RV's are acrobatic". I guess that settles it because if the FSDO says it is so, it must be true.
 
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But - I'm not sure it's really worth the effort, when RV-7's are readily available. If the RV-9 was the only Vans kit offered, there would be plenty of ACRO conversions being done.
 
Just curious about the thought process where aerobatics considered an all or none proposition. 707's have been rolled, I used to loop my Cub. Have even done a roll in my -8 that didn't exceed 1.1 gs (things to try on a long trip...). They don't all have to be high-stress maneuvers.

https://www.youtube.com/watch?v=Ra_khhzuFlE

Just sayin.
 
It's not how stressful the manoeuver is... It's how much margin you have left over when you screw up.
 
nice

Thanks Bill. Great response and good info.
I always thought that the engine mounts and the fuselages were weak on the RV-9 and that confirmed it. :)
I'm a non-aerobatic person myself so that's a non-issue for me. Building in a little extra margin is a thought but I'll just probably just motor on and try to keep the weight down.
cj


While I like the thought of this mod, I doubt it has been done. The reason is the pre-punched spar. The -7 and -9 have the same number of ribs, with more space between each on the -9. To do this, you would want to start by respacing the ribs to match that of the -7. Then you can cut down the flaps while keeping the ailerons the stock length. That right there would probably increase the stall speed to close to that of the -7.

You could take close to two feet off the wingspan by changing the wingtips.

After all that you still have a very large HS to deal with. The HS is so large to compensate for the downward pitching moment that occurs when deploying the -9's large fowler flaps.

Here is a list of just some of the reasons I have heard over the years as to why the -9 is NOT aerobic:

1. The wing is too long.
2. The flaps will fail, if you go negative.
3. He VS and rudder aren't strong enough.
4. The HS is weak.
5. The fuselage isn't designed for it.
6. The engine mount will fail.

Also, my operating limitations includes acrobatic. The FSDO inspector made a big point of telling me because he knew all "RV's are acrobatic". I guess that settles it because if the FSDO says it is so, it must be true.
 
quote
3. He VS and rudder aren't strong enough.
4
5. The fuselage isn't designed for it.
6. The engine mount will fail.

unquote

What parts of a -9 fuselage are different from a -7 fuselage (other than the wing spar carry-through)?

Aren't -9 rudders shipped with all -7 tail kits now?

Does the -9 have a different motor mount from a -320 powered -7?

But I'm not saying the -9 is a good acro platform; the G-limits would make me cautious about wing/tail strength.

When the -9 was first announced, my 1st thought was the same as Pierre; wouldn't it be nice to have a higher aspect ratio, modern airfoil wing with a -7's stall speed. Still safe landing speed & likely faster cruise at altitude. I actually mentioned it to somebody on Van's staff at SNF the year they announced the -9. It's nice to see that they finally acted on my suggestion (RV-14...).

Charlie
;-)
 
Thanks Bill. Great response and good info.
I always thought that the engine mounts and the fuselages were weak on the RV-9 and that confirmed it. :)
...
cj

You read too much into my post. That is simply a list of things I have heard and/or been told over the years by various people. I wouldn't say they are bases on factual data. Call them "rumors".

The -9's fuselage and engine mount are identical to the -7's, except for the spar center section, seat ribs, etc. (There are slight differences, such as the angle the landing gear exits the mount to accommodate the -9's longer landing gear which is required to get the wing stalled in the three point attitude.) In fact most of the -9's fuselage is made with -7 parts. (The first digit of the part number indicates what plane it came from. The -9 uses -4 aileron bell cranks, -6 firewall, -7 tailcone, etc.)
 
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... I actually mentioned it to somebody on Van's staff at SNF the year they announced the -9. It's nice to see that they finally acted on my suggestion (RV-14...).

Charlie
;-)

The -14 doesn't use that amazing Roncz airfoil that is used on the -9. However, they did add the fowler flaps to help lower the stall speed.
 
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10/4

Bill,
I was just kidding. Guess the :) face didn't indicate that.
Yea, I heard those same things about the structure among other things.
cj

You read too much into my post. That is simply a list of things I have heard and/or been told over the years by various people. I wouldn't say they are bases on factual data. Call them "rumors".

The -9's fuselage and engine mount are identical to the -7's, except for the spar center section, seat ribs, etc. (There are slight differences, such as the angle the landing gear exits the mount to accommodate the -9's longer landing gear which is required to get the wing stalled in the three point attitude.) In fact most of the -9's fuselage is made with -7 parts. (The first digit of the part number indicates what plane it came from. The -9 uses -4 aileron bell cranks, -6 firewall, -7 tailcone, etc.)
 
The -9 also has a much different horizontal stabilizer and elevators than the -7 as well. The -9's horizontal is wider and a rectangular/hershey-bar planform, the -7's is a shorter, tapered planform.
 
I have witnessed a -9 doing a roll. Looks like they roll very well. Haven't done it myself. Probably will someday. Curious how many G's are pulled during it?
 
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I have witnessed a -9 doing a roll. Looks like they roll very well. Haven't done it myself. Probably will someday. Curious how many G's are pulled during it? Bill R. any ideas on that? Not that you would have any first-hand knowledge.;)

A roll is a 1G maneuver when done right, BUT if done incorectly you would exceed the G limit in the recovery....
 
I have witnessed a -9 doing a roll. Looks like they roll very well. Haven't done it myself. Probably will someday. Curious how many G's are pulled during it? Bill R. any ideas on that? Not that you would have any first-hand knowledge.;)

As much or little as you want. I assume you will learn some bare basic aerobatic concepts and get some training before "probably someday" rolling your -9? :)
 
As much or little as you want. I assume you will learn some bare basic aerobatic concepts and get some training before "probably someday" rolling your -9? :)

Agreed. A 'simple' roll when done improperly, or without proper training, can get you in real trouble. A split-s...is one way...
 
I'm glad to see the comments in this thread come back around to the important consideration....
Not, can an RV-9 do aerobatics, but should you do it in one.

With all of the passionate comments regarding A model nose gears and that they don't have enough margin for error...
Comments like, "I don't want a gear system that requires me to be perfect all the time".
or, "A day may come when I make a mistake".
It amazes me how casually people are willing to give up some of the margin that assures the tail, wings, and all the rest of the parts stay attached

Shouldn't that same attitude be applied to aerobatics?

Sure, an RV-9(A) can do aerobatics, but the margin for error is reduced by at least a third (maybe more depending on the situation). If you are good all the time, it may not be an issue.


If you are not....
 
A 'simple' roll when done improperly, or without proper training, can get you in real trouble. A split-s...is one way...

Even after performing countless numbers of rolls successfully in RVs and thinking you know what you're doing, you'd be surprised how easy it is to botch one and end up coming out in a split-s. Don't ask me how I know :eek:
 
Which type of roll?
Aileron rolls easy peazy in an RV.

A good barrel roll (most people don't know what that is and RV's let you get away with lousy ones), is not so easy.

I have done a split S out of both. Foolishly tried to aileron roll my first Aeronca and didn't have the momentum to pull the nose high enough. No G meter but I was lucky. The wings stayed on. By the way, it was certified and flight tested for aerobatics. I had some training and experience, but the Aeronca ain't no Bucker.

In the RV, chasing tail in trail with some formation buddy's when lead botched a barrel roll, followed right by me botching it (always follow your lead right?). 4.5G's in the recovery and pushing Vne. Flight tested for aerobatics and documented in OP's limits.

If I was to consider rolling an RV9 ( and I woudnt), it would be an aileron roll only, but I don't have Sean Tucker's skill set, not even close. I did meet him and had the honor of holding the ribbon pole for him. Does that count?
 
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Even after performing countless numbers of rolls successfully in RVs and thinking you know what you're doing, you'd be surprised how easy it is to botch one and end up coming out in a split-s. Don't ask me how I know :eek:

This is no way advocates acro in the -9, but I really can't understand how you could perform such a blunder - as in accidentally stop the roll and split-S a basic +G aileron roll after doing "countless" of them (assuming you had a little bare basic understanding of aerobatics and why this should never be done). It's literally the easiest maneuver you can do in an airplane with decent roll rate like an RV. Yes, you really can do 10,000 out of 10,000 successfull rolls at very low G, perfectly safely without needing a fraction of the skills of certain famous airshow pilots. The split-S roll is something that absolute beginners do when they freeze inverted. Not trying to flame you, I have just never heard of anyone doing this after gaining some minimal knowledge and comfort level. It's almost the equivalent of saying "even after performing countless successful landings, you'd be surprised how easy it is to panic and push forward rather than pull back during the roundout".

Even airplanes stressed for aerobatics will not necessarily protect pilots from their own blunders.
 
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No acro should be attempted without training.

Even a simple aileron roll can go bad in two ways.

1. The pilot panics and yanks back on the stick while inverted. This is a split S and you WILL find yourself well past Vne. If you pull on the stick to get out of the ensuing dive, you WILL remove parts from the plane.

2. Exiting nose low. This usually happens when you don't get the nose high enough to start with. If you don't have the altitude to start with, this can be fatal. With altitude, this isn't a big issue.
 
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What's the problem? Inverted flight, flat spins, tail slides, hammerheads, loops all day long.

(The 1:1-scale version will remain right-side up, though.)

 
A couple 'o things:

1) Citabrias must be bad, maybe even dangerous, for aerobatics, as they are only utility category airplanes being rated at +5/-2g's ;)

2) FAR 23.3 states: "(b) The utility category is limited to airplanes that have a seating configuration, excluding pilot seats, of nine or less, a maximum certificated takeoff weight of 12,500 pounds or less, and intended for limited acrobatic operation. Airplanes certificated in the utility category may be used in any of the operations covered under paragraph (a) of this section and in limited acrobatic operations."

3) FAR 23.151 states: "?23.151 Acrobatic maneuvers.
Each acrobatic and utility category airplane must be able to perform safely the acrobatic maneuvers for which certification is requested. Safe entry speeds for these maneuvers must be determined"

4) FAR 23.221 states: "(b) Utility category airplanes. A utility category airplane must meet the requirements of paragraph (a) of this section. In addition, the requirements of paragraph (c) of this section and ?23.807(b)(7) must be met if approval for spinning is requested." and "(c) Acrobatic category airplanes. An acrobatic category airplane must meet the spin requirements of paragraph (a) of this section and ?23.807(b)(6). In addition, the following requirements must be met in each configuration for which approval for spinning is requested:

(1) The airplane must recover from any point in a spin up to and including six turns, or any greater number of turns for which certification is requested, in not more than one and one-half additional turns after initiation of the first control action for recovery. However, beyond three turns, the spin may be discontinued if spiral characteristics appear."

So it would seem that aerobatics should be fine as long as they are part of your test program. That said, I would like to know more about any first hand experience there is out there with spins in 9's and whether the 1 1/2 turn spin recovery requirement is what prompts Vans to prohibit spins, or if there is other behavior that drove this decision, particularly (obviously) bad behavior.

Tim
 
The split-S roll is something that absolute beginners do when they freeze inverted.

That would be me, a beginner with 6 hrs dual acro...even though I was trained not to do a split-s, I had a brain fart while doing solo acro. But...even though I was silly enough to do the ol 'roll and pull', from training...I knew what was coming and pulled power immediately. Even with that I was pushing Vne on the pullout. I had plenty of altitude so that wasn't a problem. My point is...get training, because some might think..."its just a roll, no big deal." Usually its not, it really is easy...if you don't do something stupid. Count me as being stupid...once :) Just a cautionary tale.
 
1) Citabrias must be bad, maybe even dangerous, for aerobatics, as they are only utility category airplanes being rated at +5/-2g's ;)

Utility category is +4.4 / -2.2 G's
So there goes another .6 G's of margin you were thinking you had.
 
No acto should be attempted without training.

Even a simple aileron roll can go bad three ways.

1. The pilot panics and yanks back on the stick while inverted. This is a split S and you WILL find yourself well past Vne. If you pull on the stick to get out of the ensuing dive, you WILL remove parts from the plane.

2. Exiting nose low. This usually happens when you don't get the nose high enough to start with. If you don't have the altitude to start with, this can be fatal. With altitude, this isn't a big issue.

Got a third one for you after doing a stupid once :eek:

I've been doing really basic aerobatics (loops/rolls) in the -6 since before I could land it. Took a non-pilot passenger up one day, and after letting him fly around for a couple minutes decided to demonstrate a roll. He enjoyed it, and had done well earlier, so I figured "it's just a roll, how hard can it be?"

So, I let him try. About the time we made it 160 degrees around, I start coming out of my seat fast. Woah! So I took it away and finished the roll out. Explained to him not to do that, then let him try again :eek:

It happened again, so I recovered, and decided no more rolls for him.

In hindsight, it was a really dumb thing to do. The "what if I goof it up?" part never occurred to me. I didn't realize how dumb since it seemed so simple at the time.

So, 3. Pilot panics, pushes forward, goes negative-g, and panics more. Airplane loses control.
 
Before I started flying aerobatics myself, an aerobatics instructor told me once that the most common error when doing your first rolls is that you give full control inputs as you start, but as the plane starts to roll you subconsciously ease off the inputs. That usually ends up with the stick centered and the plane inverted and not rolling anymore, usually with the nose already down a bit from the horizon because it took so long to get inverted.

Because this is such a "wrong" attitude for anyone who has seen a roll but hasn't done one of their own yet, you panic. The reflex reaction in a panic situation is to pull yourself into a ball... Arms come to the gut. Along with them, the stick goes back, and you split-S out of it.

So the mantra for me has always been... When rolling, keep rolling until you don't want to be rolling anymore.
 
Snowflake and Luddite seem to make the most sense to me.
I don't panic when I land. Don't panic when the engine stutters.
In fact, being a pilot has brought a problem solving calm to all my efforts...even outside aviation.
I suspect those that actually do roll their 9 airframes simply sit by and don't venture a comment here.
Rolling 360 is such a simple maneuver...
My first week as a skydiver pilot in the 70's..... I dumped my guys (girls were hard to find at the drop zone back then) and proceeded down for the umpteenth time.
Pulled the nose up... rolled the 182 to the left. (left handers seem to do that)
I was done in a few seconds. Sort of a hoot... but not earth shaking experience.
The gyro was a little wonky for the rest of the weekend... but who needs it right?
 
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